This invention pertains to processing paper sheets, and more particularly to apparatus that feeds and folds individual sheets of paper.
Various types of equipment have been developed that feed paper sheets to mechanisms that process the sheets in a variety of ways. For example, photocopy machines invariably include feeders that supply paper sheets to the mechanisms that produce images on the sheets.
A particularly important application of paper feeders pertains to folding and sealing machines. U.S. patent application Ser. No. 09/326,299, now U.S. Pat. No. 6,264,592 B1 describes an exemplary combination folding and sealing machine that includes a paper feeder.
It is critical in a folding machine that the paper sheets be consistently and properly fed to the folding mechanisms. For successful and economical operation, the feeder must deliver the sheets at high speed, one at a time, and properly oriented. The feeder must not allow a subsequent sheet to be propelled downstream until the previous sheet has completely left the feeder. If more than one sheet is propelled downstream at the same time, jams will occur at a downstream station. At the same time, all the sheets must be oriented such that their side edges are parallel to the direction of downstream travel. Failure to properly orient the sheets results in unacceptable misalignments in the folded sheets.
Prior equipment exists that successfully feeds paper sheets. However, the prior equipment is both complicated and expensive. For instance, one prior feeder used a solenoid that coacted with a feed wheel to propel the sheets downstream. On the other hand, there has been a long standing need for a dependable feeder for use with low cost folding and sealing machines. The advantages obtained from developing low cost folding and sealing machines is lost if the feeder is disproportionately expensive relative to the folding and sealing mechanisms.
Prior feeders suffered the further disadvantage of being able to accommodate only a single thickness of paper without adjustment. For example, U.S. Pat. Nos. 4,552,353 and 4,588,181 show sheet feeding apparatus that limits a gap between a feed roller and a pivotal friction member to a spacing corresponding to a single sheet. The 4,552,353 and 4,588,181 patents show automatic adjusting devices for maintaining a single clearance between a feed wheel and a friction member. The expense, as well as the potential unreliability, of attempting to use only a clearance equal to the thickness of one sheet makes the foregoing adjustment devices of questionable usefulness on low cost paper processing machines. A related problem was that it was awkward to adjust the prior paper feeders to accommodate different sheet thicknesses. Prior low cost paper feeders were also limited in the number of sheets that could be stacked on them.
Other paper feeders are shown in U.S. Pat. Nos. 4,896,871 and 4,991,830. Neither is suitable for reliable low cost feeding.
In accordance with the present invention, a paper folding machine includes a simple and low cost feeder that reliably propels one sheet of properly oriented paper at a time in a downstream direction. This is accomplished by apparatus that includes a gate tip that conveniently adjusts to accommodate a range of sheet thicknesses.
The paper sheets are propelled from a stack loaded at a paper supply station upstream of the gate tip. An upstream end of a tray of the paper supply station is supported for swinging on the machine frame by means of a tray shaft. The sheets are stacked on the tray such that their leading edges are under a pickoff wheel. A tray spring biases the topmost sheet of the stack into contact with the pickoff wheel at a first tangent point. Rotation of the pickoff wheel propels the topmost sheet by friction in the downstream direction to the gate tip.
The gate tip also underlies the pickoff wheel. The gate tip comprises a singulator that is pivotally connected to a ramp that in turn is attached to the frame. A singulator spring is interposed between the ramp and the singulator. The singulator spring biases the singulator to contact the pickoff wheel at a second tangent point. To limit the pivotal motion of the singulator away from the pickoff wheel, a singulator screw is threaded into the ramp. The end of the singulator screw shank is set at a selected clearance from the singulator. To provide high resolution when setting the clearance, the singulator screw longitudinal centerline does not pass through the axis of rotation of the pickoff wheel. Instead, the singulator screw longitudinal centerline is downstream of the pickoff wheel axis of rotation. The singulator can be pivoted in the second direction against the force of the singulator spring. The singulator screw is adjusted such that the clearance with the singulator is at least equal to the thickness of one of the particular paper sheets being processed, but the clearance is less than the thickness of two sheets. In some applications, a relatively soft pickoff wheel is used. In those instances, the singulator screw is adjusted such that its clearance with the singulator is slightly less than the thickness of a sheet.
The leading edge of a topmost paper sheet that is propelled by the pickoff wheel from the stack on the tray strikes the singulator slightly upstream of the second tangent point of the pickoff wheel with the singulator. Should a second sheet be propelled from the stack to the gate tip along with the topmost sheet, the second sheet cannot pass through the nip between the pickoff wheel and the singulator. That is because the clearance between the singulator screw and the singulator is less than the thickness of the two sheets. The leading edge of the second sheet will merely remain in place between the topmost sheet and the singulator until the topmost sheet trailing edge has passed completely through the nip. At that point, the clearance between the singulator screw and the singulator allows the second sheet leading edge to enter the nip and be propelled downstream.
When a relatively soft pickoff wheel is used and the clearance between the singulator screw and the singulator is less than the paper sheet thickness, the pickoff wheel compresses as a topmost sheet passes through the nip between the singulator and the pickoff wheel. The compression of the pickoff wheel is sufficient to enable the topmost sheet to be propelled through the nip. However, the pickoff wheel does not compress enough for a second sheet to pass through the nip with the topmost sheet. The second sheet remains in place between the topmost sheet and the singulator until the topmost sheet has passed completely through the nip.
The gate tip of the invention is capable of accommodating relatively wide variations of paper thickness without adjustment. For a selected clearance between the singulator and the singulator screw that suits a first sheet thickness, sheets of greater thickness up to slightly less than double the first thickness can be handled without adjustment. On the other hand, when adjustment is necessary for the clearance, the singulator screw is easily accessible for quick and easy adjustment.
The present invention is also concerned with proper feeding of the paper sheets regardless of the number of sheets loaded at the paper supply station. Loading a stack of sheets on the tray causes the tray downstream end to swing downwardly in an arc through a tray swing angle about a tray shaft against the force of the tray spring. The plane of the topmost sheet in the stack therefore makes an angle in space that depends on the number of sheets in the stack. The first tangent point of contact between the topmost sheet and the pickoff wheel changes as the number of sheets changes. As a result, the angle about the pickoff wheel axis of rotation subtended by the first and second tangent points also varies. Another consequence of the variable location of the first tangent point is that the leading edge of a sheet strikes the singulator at an angle that is dependent on the number of sheets loaded on the tray. The gate tip of the invention successfully allows for the variation in the various geometric relations among the sheets, pickoff wheel, and singulator caused by loading different quantities of paper at the paper supply station.
Further in accordance with the present invention, the paper feeder propels the sheets in the downstream direction in a perfectly oriented manner. That is, the side edges of the sheets are parallel to the downstream direction of the sheets. To obtain proper sheet orientation, the paper folding machine includes a skew compensator. The skew compensator comprises a pivot bracket mounted to the tray shaft. The upstream end of the tray rests on the pivot bracket. The tray is connected to the bracket for rotating about a bracket axis that is generally perpendicular to the downstream direction. A side bracket is also fixed to the tray shaft. A compensator screw passing through the side bracket mates with threads in the tray. Turning the compensator screw causes the tray to rotate about the bracket axis. In that manner, the tray can be rotated to properly orient the sheets for downstream feeding.
As mentioned, the tray downstream end swings downwardly in an arc about a tray shaft against the force of the tray spring when a stack of papers is loaded on the tray. To prevent the stack from sliding off the tray downstream end, as well as to keep the leading edges of the sheets in alignment, the paper feeder includes a plate adjacent the tray downstream end. The plate is generally tangent to the arc through which the tray downstream end swings. In a preferred embodiment, the plate is part of the ramp to which the singulator is connected. The ramp plate and the downstream end of the tray cooperate such that a stack of sheets need not be fanned before it is loaded on the tray.
It is a further feature of the invention that the paper feeder is easily integrated into the paper folding machine. In fact, the feeder is ideal as an integral part of a low cost folding machine. The paper sheets propelled downstream by the feeder are folded and discharged as completed forms at the downstream end of the machine. The completed forms are propelled by belts on which the forms ride. An important aspect of the invention is that the conveyor belts do not wander laterally during operation. To prevent belt wander, the belt drive shaft is grooved. The shaft grooves receive the belts and guide them laterally. To provide additional belt guidance, the shaft grooves are crowned.
The method and apparatus of the invention, using an easily adjustable gate tip and a skew compensator, thus reliably supplies sheets one at a time to paper processing equipment. The probability of misfeeding or misfolding a sheet is remote, even though the paper feeder is inexpensive to manufacture and convenient to operate.